/* * Copyright (C) 2002-2015 The DOSBox Team * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * ... */

This may be true, except to the best of my knowledge as you point out, DOSBox is 'GPLV2+', i.e. GPLV2 with the "or (at your option) any later version." clause left intact.However, as a whole, DOSBox is licensed (currently) GPLV2, so any xBR/xBRZ stuff which is licensed either GPLV3 or LGPLV3 is incompatible with the current distribution of DOSBox, unless DOSBox changes its entire license to GPLV3.(any xBR/xBRZ stuff which is licensed GPLV2 or LGPLV2.1 is fine, though)

Due to the fact that certain distributors (Steam, (and MAYBE HumbleBundle?)) use DRM/TiVo-ization and distribute certain games with DOSbox packages (with sources included), changing the license to GPLV3 might hurt the project significantly.

Lord Nightmare wrote:I've also (unlike HQX) yet to see a full mathematical description of the xBR/xBRZ algorithms which would allow a separate, permissively licensed code version to be created from scratch and not run into problems inherent in 'looking at GPL code to write BSD/MIT code'

Hence, I'm avoiding xBR until I can see a textual description of how it works.

Well, that's a start, at least. The post looks similar to the one that was deleted with a forum purge at byuu's old forums, but looks only about 1/2 complete description of the algorithm.

What I find far more useful however is that Hyllian seems to have relicensed about half of the xBR code at https://github.com/libretro/common-shad ... br/shaders as MIT. There are still a bunch of GPLv2 bits mixed in there, but the MIT parts are definitely usable to me.

Binet wrote:ZenJu, the results look very impressive. How does the algorithm work?

Have a look at the code. It's beautiful. Generally speaking it does a pattern matching, but in contrast to HQx it does not check against a list of specific patterns, but a only small set of highly generic patterns. Thous the better overall result. The seamless alpha-blending of the output geometry also doesn't hurt.